1. Field of the Invention
The present invention relates to an apparatus for etching, which is used in the manufacturing processes of semiconductor elements such as ICs and LSIs and more particularly to a reactive ion etching apparatus.
2. Description of the Prior Art
Heretofore, in the method for manufacturing semiconductor elements such as ICs and LSIs, there has been adopted a photolithography technique for forming patterns which comprises the steps of applying, onto the surface of a substrate to be processed, a radiation-sensitive resin such as a negative-working photoresist composed of a cyclized substance of polyisoprene and a bisazide or a positive-working photoresist composed of a novolak resin and a quinonediazide compound, exposing the radiation-sensitive layer to g-line (wave length: 436 nm) or i-line (wave length: 365 nm) of a mercury lamp and developing the radiation-sensitive layer with a developer to form a desired pattern.
In this connection, LSIs have been made finer recently and thus the minimum dimension of patterns to be formed on a substrate has been decreased to submicron region. In the formation of patterns having such a fine dimension, a problem that sufficient resolution cannot be attained arises due to the influence of reflection of light during the exposure, shallow focal depth of the exposure system used, if a conventional photolithography technique is employed in which a developer is used to develop patterns, in particular in the case where a topographic substrate having step structure is used.
As a means for solving such a problem, there has been proposed a dry developing process which comprises etching a resist layer applied to a substrate to form a desired resist pattern utilizing a reactive ion etching apparatus for generating gas plasma such as oxygen gas plasma in place of developing the resist layer with a developer to obtain a desired pattern as in the photolithography method explained above (see Laid-open Japanese Patent Application Publication (hereinafter referred to as "J.P. KOKAI") No. 61-107346 or the corresponding European Laid-Open Patent Application No. 184,567).
As such a reactive ion etching apparatus, there is disclosed, in J.P. KOKAI No. 58-151028 or the corresponding U.S. Pat. No. 4,422,896 and J.P. KOKAI No. 59-140375 (or U.S. Pat. No. 4,581,118 corresponding thereto), a reactive ion etching apparatus having a built-in means for generating a magnetic field parallel to the surface of a material to be etched, the means being disposed on a negative electrode to which microwave power is applied and which serves as a support for the material to be etched.
On the other hand, J.P. KOKAI No. 58-170016 discloses a reactive ion etching apparatus which is equipped with a means for generating a magnetic field perpendicular to the surface of a negative electrode serving as a support for a material to be etched.
These reactive ion etching apparatuses make it possible to increase the concentration of reactive species present in the gas plasma generated therein. Therefore, the use of such apparatuses makes it possible to perform the etching procedure more rapidly compared with the use of a common parallel plate type reactive ion etching apparatus.
However, in such apparatuses, rapid etching can be achieved by increasing the electric voltage to be applied thereto, but on the other hand, problems such that a material to be etched is impaired during the etching process and that the materials cause deformation or property modification due to heat generated and/or applied thereto during the etching procedure arise.
Moreover, in the formation of resist patterns utilizing a bilayer resist or a trilayer resist and the aforementioned dry development technique in which desired resist patterns are formed by selectively diffusing, into the areas on which the desired resist patterns are formed, an organic silicone compound such as those disclosed in J.P. KOKAI No. 61-107346 to thus form an etch barrier having enhanced resistance to etching, it is impossible to select a sufficient selective etching ratio between the portions to be etched and those serving as the etching barrier and, therefore, a rapid etching process cannot be carried out when these reactive ion etching apparatuses are used as a dry developing apparatus in which oxygen plasma is generated and used. Moreover, a line width control of resist patterns becomes insufficient due to the difference between the etching rate of portions of the material to be etched in the vicinity of wafer chucks and that of the other portions thereof. In addition, since in the conventional means for supporting a wafer, the surface of the wafer is directly clamped, particles are formed on the surface of a wafer.
The present invention relates to an apparatus for etching, which is used in the manufacturing processes of semiconductor elements such as ICs and LSIs and more particularly to a reactive ion etching apparatus.